It is known to provide a boosted engine of a motor vehicle with a charge cooler to cool the air before it is inducted into the engine. In a conventional arrangement the air charge cooler (often referred to as an intercooler) is mounted at the front of the motor vehicle and the charge air is cooled by air passing over it as the motor vehicle moves through the air. Such intercoolers need to be large due to their low efficiency and are difficult to package on the motor vehicle. Such intercoolers generally require a large diameter air flow conduit extending from the front of the vehicle to the engine and the source of charge air. Furthermore, unless a means to force air through the intercooler is provided, the amount of cooling available may be limited when the motor vehicle is stationary or travelling at low speed. In addition, the amount of cooling available is affected by the temperature of the ambient air passing through the charge cooler and so, when the engine must operate at high load in a high ambient temperature, a larger charger cooler has to be used than is necessary for operation in a lower ambient temperature.
To overcome such problems it is known to provide an air-to-liquid type of heat exchanger often referred to as a Water Cooled Charge Air Cooler (WCCAC) to cool the charge air before it is drawn into the engine. With such a WCCAC cooler the charge air passes through an enclosed box or housing to cool the air. The housing contains a heat exchanger having a number of passages through which liquid coolant passes and fins thermally coupled to the passages over which the charge air passes to cool it.
Such known heat exchangers are normally rectangular or square in shape and the charge air flow area of the heat exchanger where the charge air enters the heat exchanger is substantially the same as the charge air flow area where the charge air exits the heat exchanger.